Electrical stimulation system

ABSTRACT

Provided are an electrical stimulation device configured so that a correspondence among finger motion and electrodes can be clarified in a short amount of time regardless of the state of attachment to a user&#39;s arm and an individual difference and an intended finger can be driven at high accuracy with very few erroneous operation and an electrical stimulation system using the electrical stimulation device. When an electrode probability matrix in which a Bayesian posterior probability indicating an electrode-finger correspondence is described as an element is updated in a host, the position of an element positioned on the upper left side of the electrode probability matrix and indicating that finger motion occurs is compared to rearrange the columns of the electrode probability matrix as necessary.

TECHNICAL FIELD

The present invention relates to an electrical stimulation deviceconfigured to provide an electrical stimulation signal to a muscle of anarm of a person and detect displacement of the muscle of the arm by asensor and an electrical stimulation system having a combination of theelectrical stimulation device and an information processing device.

BACKGROUND ART

Typically, an attempt has been made to move a finger or a hand of a userby a command from the outside in such a manner that multiple electrodesare attached to a forearm of a person (the user) to provide electricalstimulation signals to muscles of the forearm. For example, it has beenconsidered that, e.g., rehabilitation, training, and motion assistanceof fingers are performed by the command from the outside. Moreover, ithas been also proposed that when, e.g., a head-mounted display is usedto execute the virtual reality processing (Virtual Reality) of providingthe user with a virtual space image or the augmented reality processing(Augmented Reality) of superimposing a virtual object image on an actualspace video, fingers are moved in association with, e.g., a virtualspace video based on the command from the outside to enhance reality.

The inventors of the present application have proposed an electricalstimulation device as described in advance in Patent Literature 1. Theelectrical stimulation device proposed in Patent Literature 1 is adevice configured such that multiple electrodes are attached to a bandto be attached to a forearm of a user to provide electrical stimuli tomuscles of the forearm.

CITATION LIST Patent Literature

-   PATENT LITERATURE 1: JP-A-2014-104241

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

The user wearing the electrical stimulation device proposed in PatentLiterature 1 moves one's finger or hand by the electric stimuli providedto the muscles of the forearm according to a command from the outside.For example, the muscles of the forearm for moving five fingers bystimulation are known in advance, and the electrode attached to theelectrical stimulation device is used to stimulate a specific muscle tomove the finger corresponding to such a muscle.

A situation is assumed, in which the user wears a band-shaped electricalstimulation device on the forearm. In this situation, the band-shapedelectrical stimulation device includes multiple electrodes, but acorrespondence between the electrode and the muscle needs to be sensed.For such sensing, when the user wears the band-shaped electricalstimulation device, a calibration process needs to be first performed tooutput an electrical stimulation signal from each electrode and tocheck, in advance, which finger moves.

That is, when the user wears the band-shaped electrical stimulationdevice, the electrical stimulation device needs to accurately grasp, inadvance, to which muscle each electrode arranged at the electricalstimulation device corresponds. For this reason, the calibration processhas a significantly important meaning.

A person arm thickness greatly varies according to an individualdifference such as an age, a gender, and a body weight. For this reason,for absorbing the individual difference in the arm thickness only by asingle electrical stimulation device, a greater number of electrodes andsensors than the number of fingers, i.e., five fingers, needs to beprovided. Accordingly, some electrodes do not correspond to fingermotion. That is, for accurately operating the electrical stimulationdevice, the correspondence between the muscle for actually moving thefinger and the electrode needs to be clarified in advance by thecalibration process.

The present invention has been made in view of the above-describedproblems, and is intended to provide an electrical stimulation deviceconfigured so that a correspondence among finger motion and electrodescan be clarified in a short amount of time regardless of the state ofattachment to a user's arm and an individual difference and an intendedfinger can be driven at high accuracy with very few erroneous operationand an electrical stimulation system using the electrical stimulationdevice.

Solution to the Problems

For solving the above-described problems, the electrical stimulationdevice of the present invention includes a band to be wound around anarm of a user, multiple electrodes arranged on one surface of the band,a multiplexor configured to select one of the multiple electrodes, anear field communication receiving unit configured to receive a commandfor moving a finger from a host, an electrode probability matrixconfigured such that a correspondence among finger motion and themultiple electrodes is described in terms of probability, and afinger-electrode correspondence conversion unit configured to specify,based on the command for moving the finger, an electrode with themaximum probability from the electrode probability matrix and to controlthe multiplexor to select the specified electrode.

Effect of the Invention

According to the present invention, the electrical stimulation deviceconfigured so that the correspondence among finger motion and theelectrodes can be clarified in a short amount of time regardless of thestate of attachment to the user's arm and the individual difference andthe intended finger can be driven at high accuracy with very fewerroneous operation and the electrical stimulation system using theelectrical stimulation device can be provided.

Other problems, configurations, and advantageous effects than above willbe apparent from description of an embodiment below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an outer appearance of an electricalstimulation device as an example embodiment of the present invention;

FIG. 2 is a plan view of an electrode arrangement surface;

FIG. 3 is a view of a state right before and right after the electricalstimulation device is attached to a forearm;

FIG. 4 is a schematic view of an electrical stimulation system havingthe electrical stimulation device as one example of a usage pattern ofthe electrical stimulation device;

FIG. 5 is a block diagram of a hardware configuration of a host;

FIG. 6 is a block diagram of a hardware configuration of the electricalstimulation device;

FIG. 7 is a block diagram of software functions of the electricalstimulation device and the host in a normal mode;

FIG. 8 is a block diagram of the software functions of the electricalstimulation device and the host in a calibration mode;

FIG. 9 is a time chart of the flow of calibration operation executed bythe electrical stimulation device and the host in the calibration mode;

FIG. 10 is a flowchart for describing the flow of operation in aninitial learning mode executed by the host when a user wears theelectrical stimulation device on the arm for the first time;

FIG. 11 is a time chart for describing an electric stimulus, a musclecontraction state, and muscle displacement sensor operation;

FIG. 12 is a view for describing a finger behavior matrix indicatingfinger motion in response to the electrical stimulus, a view of theprocedure of selecting an effective electrical stimulus from the fingerbehavior matrix, a view for describing a flag matrix indicating a resultof selection of the effective electrical stimulus from the fingerbehavior matrix, and a view of an electrode probability matrix generatedfrom the flag matrix:

FIG. 13 is a flowchart for describing the flow of operation in a secondlearning mode or later executed by the host when the user wears theelectrical stimulation device for the second time or later;

FIG. 14 is a flowchart for describing the flow of operation in thesecond learning mode or later executed by the host when the user wearsthe electrical stimulation device for the second time or later;

FIG. 15 is a schematic view for describing an arrangement relationshipamong arm muscles and electrodes when the user wears the electricalstimulation device on the arm for the first time, and a schematic viewfor describing the arrangement relationship among the arm muscles andthe electrodes when the user again wears the electrical stimulationdevice on the arm;

FIG. 16 is a view of an example of the finger behavior matrix producedin the second learning mode or later, a virtual electrode probabilitymatrix produced based on the finger behavior matrix, an electrodeprobability matrix stored in the host before application of the learningmode, and rearranged rows and columns of the electrode probabilitymatrix; and

FIG. 17 is a view of one example of a generalized electrode probabilitymatrix.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1 is a perspective view of an outer appearance of an electricalstimulation device 100 as an example embodiment of the presentinvention.

The electrical stimulation device 100 includes a V-shaped band 101. Theband 101 is made with, e.g., a resin sheet of silicone rubber exhibitingflexibility. Both wing portions of the band 101 are in a shape inclinedat an equal inclination angle θ1, θ2 from a horizontal line L105. Theinclination angles θ1, θ2 are 32°, for example. A rectangular circuithousing box 103 is provided on a front-surface-side center portion ofthe band 101. The circuit housing box 103 includes, for example, alater-described built-in arithmetic processing unit 150 (see FIG. 4) anda built-in secondary battery.

A first serial interface terminal 104 is provided on one short-sidesurface of the circuit housing box 103. The first serial interfaceterminal 104 is, for example, a micro USB terminal. The electricalstimulation device 100 charges the not-shown built-in secondary batteryvia the first serial interface terminal 104. Moreover, the first serialinterface terminal 104 is connected to a personal computer etc. so thatfunction extension such as updating of firmware as a component of thearithmetic processing unit is available.

A back surface (a lower surface in FIG. 1) of the band 101 on theopposite side of the surface to which the circuit housing box 103 isattached is an electrode arrangement surface 100 a described later withreference to FIG. 2.

As described later with reference to an attachment example of FIGS. 3Aand 3B, the electrical stimulation device 100 is attached to a user insuch a manner that the electrode arrangement surface 100 a as the backsurface of the band 101 is wound around the forearm of the user.

FIG. 2 is a plan view of the electrode arrangement surface 100 a.

The electrode arrangement surface 100 a includes electrodes 201 to 208configured to provide electrical stimulation signals to muscles of theforearm of the user, and electrodes 211 to 213, 216, 217 as groundelectrodes paired with the electrodes 201 to 208 upon use. Note that thecommon ground electrode is used for multiple opposing electrodes, andtherefore, the number of electrodes 201 to 208 and the number ofelectrodes 211 to 213, 216, 217 are not necessarily coincident with eachother.

In addition, the electrode arrangement surface 100 a includes muscledisplacement sensors 221 to 228 configured to detect motion of themuscles of the forearm of the user.

A right electrode arrangement spot 231 is provided on the right side (onthe left side in the figure) of the electrode arrangement surface 100 a,and four electrodes 201, 202, 211, 212 are arranged at the rightelectrode arrangement spot 231. Of four electrodes 201, 202, 211, 212,the electrode 201 is a first electrode, and the electrode 202 is asecond electrode. Moreover, the electrode 211 is a ground electrodefacing the electrode 201, and the electrode 212 is a ground electrodefacing the electrode 202.

The electrode 201 and the electrode 211 are electrodes configured toprovide stimuli to the muscles of the forearm, and upon attachment, arearranged adjacent to each other in a longitudinal direction L of thearm.

The electrode 202 and the electrode 212 are also electrodes configuredto provide stimuli to the muscles of the forearm, and are substantiallyrectangular electrodes arranged with these electrodes being inclinedwith respect to a circumferential direction H at the inclination angleθ2. The electrode 202 and the electrode 212 are arranged adjacent toeach other in the longitudinal direction L of the arm.

A central electrode arrangement spot 232 is provided at the center ofthe electrode arrangement surface 100 a, and five electrodes 203, 204,205, 208, 213 are arranged at the central electrode arrangement spot232. Of five electrodes 203, 204, 205, 208, 213, the electrode 203 is athird electrode, the electrode 204 is a fourth electrode, and theelectrode 205 is a fifth electrode. These three electrodes 203, 204, 205extend in the longitudinal direction of the arm, and are arrangedsubstantially in parallel with each other in the circumferentialdirection of the arm. Moreover, the electrode 208 is an eighthelectrode. The electrode 208 is an electrode elongated in thecircumferential direction of the arm. The electrode 213 is a groundelectrode commonly used for the opposing electrodes 203, 204, 205, 208.

The electrode 203, the electrode 204, and the electrode 205 areelectrodes configured to separately provide stimuli to different musclesof the forearm according to a channel, and the electrode 213 is commonlyused as a ground electrode. Three electrodes 203, 204, 205 are arrangedin the circumferential direction H of the arm, and the electrode 213 asthe common ground electrode arranged adjacent to three electrodes 203,204, 205 in the longitudinal direction L is a rectangular electrodeelongated in the circumferential direction H of the arm.

The electrode 208 is a rectangular electrode elongated, adjacent to theelectrode 213, in the circumferential direction H of the arm. Theelectrode 213 is also used as the ground potential of the electrode 208.Note that the electrode 208 is an electrode used as backup. Theelectrode 208 is elongated in the circumferential direction H of thearm, and therefore, stimuli can be simultaneously provided to multiplemuscles of the arm.

A left electrode arrangement spot 233 is provided at a left portion 102(on the right side in FIG. 2) of the electrode arrangement surface 100a, and four electrodes 206, 207, 216, 217 are arranged at the leftelectrode arrangement spot 233. Of four electrodes 206, 207, 216, 217,the electrode 206 is a sixth electrode, and the electrode 207 is aseventh electrode. Moreover, the electrode 216 is a ground electrodefacing the electrode 206, and the electrode 217 is a ground electrodefacing the electrode 207.

The electrode 206 and the electrode 216 are electrodes configured toprovide stimuli to the muscles of the forearm, and are substantiallyrectangular electrodes arranged with these electrodes being inclinedwith respect to the circumferential direction H at the same angle θ1 asthe inclination angle θ1 of the left portion 102.

The electrode 207 and the electrode 217 are electrodes configured toprovide stimuli to the muscles of the forearm, and upon attachment, arearranged adjacent to each other in the longitudinal direction L of thearm.

The muscle displacement sensors 221, 222 are arranged at two spots inthe vicinity of the right electrode arrangement spot 231 of theelectrode arrangement surface 100 a. The muscle displacement sensors223, 224, 225, 226 are arranged at four spots in the vicinity of thecentral electrode arrangement spot 232 of the electrode arrangementsurface 100 a. The muscle displacement sensors 227, 228 are arranged attwo spots in the vicinity of the left electrode arrangement spot 233 ofthe electrode arrangement surface 100 a.

Eight muscle displacement sensors 221 to 228 are well-knownphotoreflectors. Each of these muscle displacement sensors includes aninfrared light emission element 221 a to 228 a and an infrared lightreceiving element 221 b to 228 b (see FIG. 6), and is configured todetect a change in a distance from a muscle displacement sensorarrangement surface to a surface of the muscle of the arm. The infraredlight emission elements 221 a to 228 a are, for example, near infraredLEDs, and the infrared light receiving elements 221 b to 228 b are, forexample, phototransistors.

When the muscle contracts, the distance between the photoreflector andthe surface portion of the muscle fluctuates due to a projection of askin portion of the muscle. The photoreflector detects, by thephototransistor, the intensity of reflected near infrared light inassociation with such distance fluctuation. The near infrared lightexhibits the property of penetrating a skin surface, and therefore, issuitable for detection of a projecting state of the muscle.

Note that a resin material (not shown) exhibiting adhesion is arrangedat other spots of the electrode arrangement surface 100 a than the rightelectrode arrangement spot 231, the central electrode arrangement spot232, and the left electrode arrangement spot 233, and the adhesion ofthe resin material allows the electrode arrangement surface 100 a to beattached in a state of being wound around the forearm.

[2. Attachment Example of Electrical Stimulation Device 100]

FIG. 3A is a view of a state right before the electrical stimulationdevice 100 is attached to the forearm.

FIG. 3B is a view of a state right after the electrical stimulationdevice 100 has been attached to the forearm.

As illustrated in FIG. 3A, a center portion of the electrode arrangementsurface 100 a (FIG. 2) of the band 101 is in contact with a spot closeto the wrist of the forearm RA of the right arm of the user. In thisstate, the palm is at such a position that the palm faces up asillustrated in FIG. 3A. Moreover, the circuit housing box 103 at thecenter of the substantially V-shaped band 101 faces a palm side.

Then, the user performs the process of winding both wings of the band101 around the wrist as indicated by an arrow F1 and an arrow F2.

In this manner, the electrical stimulation device 100 is attached in astate of being wound around the forearm RA as illustrated in FIG. 3B. Inthis state, the adhesion of the adhesive resin material arranged on theelectrode arrangement surface 100 a maintains a winding state around theforearm RA.

Note that the winding state around the forearm RA only by the adhesionof the resin material is one example. For example, some kind of clipmechanism may be provided at both ends of the band 101 to hold theseportions in an overlapping state.

As described above, the electrical stimulation device 100 is attachedwith the band 101 being wound around the forearm RA, and therefore, canbe easily attached. Moreover, the band 101 is in the substantiallyV-shape. Thus, the user can easily recognize an attachment direction,and can reliably wear the electrical stimulation device 100 in a givendirection as illustrated in FIG. 3B.

Note that the example where the electrical stimulation device 100 isattached to the right arm of the user is illustrated in FIG. 3, but theelectrical stimulation device 100 may be attached to the left arm.

As illustrated in FIGS. 3A and 3B, the electrical stimulation device 100according to the embodiment of the present invention is wound around thespot close to the wrist of the forearm RA of the user. However, a markfor fixing the electrical stimulation device 100 at a fixed position ofthe forearm RA of the user in this state is not provided at the forearmRA. That is, every time the user wears the electrical stimulation device100 on the forearm RA, an attachment position is often slightly shifted.For this reason, every time the user wears the electrical stimulationdevice 100 on the forearm, a relative position relationship among theelectrodes and the muscle displacement sensors provided on the electrodearrangement surface 100 a of the electrical stimulation device 100 andthe muscles of the arm of the user is shifted.

In response to such “shift,” the present invention has been made forsuch a purpose that the electrical stimulation device 100 accuratelygrasps a correspondence among the electrodes and finger motion.

[Usage Pattern of Electrical Stimulation Device 100]

FIG. 4 is a schematic view of an electrical stimulation system 400having the electrical stimulation device 100 as one example of a usagepattern of the electrical stimulation device 100.

The electrical stimulation device 100 has a near field communicationfunction such as the Bluetooth (registered trademark) as describedlater. By, e.g., a personal computer including a near fieldcommunication function equivalent to that of the electrical stimulationdevice 100 or connection of peripheral equipment providing a near fieldcommunication function with a personal computer, the electricalstimulation device 100 establishes bidirectional communication with thepersonal computer by near field communication. Hereinafter, the personalcomputer configured to establish bidirectional communication with theelectrical stimulation device 100 by near field communication will bereferred to as a “host 401.” In FIG. 4, a near field communication unit402 is connected to the host 401, and bidirectional communication withthe electrical stimulation device 100 is established.

An application program such as a shooter game is in operation in thehost 401. According to user's operation for the application program, thehost 401 transmits a command for providing an electrical stimulus to apredetermined muscle of the user to the electrical stimulation device100 via near field communication. Based on the electrical stimulationcommand received from the host 401, the electrical stimulation device100 provides the electrical stimulus to the desired muscle of the user.

Moreover, the electrical stimulation device 100 transmits, as digitaldata, information on displacement of the muscle of the arm of the userto the host 401 by the above-described muscle displacement sensors.

Driving of the muscle displacement sensors includes driving for lightemission from the infrared LEDs, accompanied by relatively-great powerconsumption. For this reason, for acquiring the arm muscle displacementinformation from the electrical stimulation device 100 with the minimumpower consumption, the application program of the host 401 transmits,according to the state thereof, a command for driving and stopping themuscle displacement sensors to the electrical stimulation device 100.That is, the host 401 does not allow the electrical stimulation device100 to drive the muscle displacement sensors until a situation where theapplication program needs the user arm muscle displacement informationis brought during execution of the application program. At the time ofbringing the situation where the application program needs the user armmuscle displacement information, a command for driving the muscledisplacement sensors is transmitted from the host 401 to the electricalstimulation device 100. In response to the command from the host 401,the electrical stimulation device 100 drives the muscle displacementsensors to acquire the arm muscle displacement information.

At the time of terminating acquisition of the necessary arm muscledisplacement information by the application program, the host 401transmits a command to the electrical stimulation device 100 to stopdriving of the muscle displacement sensors. In response to the commandfrom the host 401, the electrical stimulation device 100 stops drivingof the muscle displacement sensors.

That is, the electrical stimulation device 100 functions as an inputdevice configured to collect the user arm muscle displacementinformation for the host 401 and an output device configured to providedisplacement to the arm muscles. It can be also said that the electricalstimulation device 100 is a terminal for the host 401 and/or theapplication program.

As described with reference to FIG. 2, eight electrodes are, excludingthe around electrodes, present on the electrode arrangement surface 100a of the electrical stimulation device 100. On the other hand, a humanhand has five fingers. This is because the number of electrodesexceeding the number of fingers, i.e., five fingers, is provided toabsorb an individual difference in a person's arm thickness only by thesingle electrical stimulation device 100. That is, eight electrodesinclude those not corresponding to motion of the fingers. Depending onthe state of attachment of the electrical stimulation device 100 to theuser's arm, the shift of a muscle position relative to the electrodeoften occurs due to shift of the attachment position. The number ofelectrodes exceeding the number of fingers, i.e., five fingers, ispreferably provided so that the electrodes can be provided correspondingto the muscles even when such shift occurs.

For accurately operating the electrical stimulation device 100, acorrespondence among the muscles for actually moving the fingers, theelectrodes, and the muscle displacement sensors needs to be clarified bya calibration process.

For this reason, there are, as operation modes of the electricalstimulation device 100 according to the embodiment of the presentinvention, two types of operation modes including a normal mode foroperation as the terminal for the application program and a calibrationmode for carrying out the calibration process of clarifying thecorrespondence among the muscles for actually moving the fingers, theelectrodes, and the muscle displacement sensors.

Note that in a block diagram for later describing software functions,the normal mode and the calibration mode will be separately described.The present invention is an invention specifically relating to thecalibration mode of these modes.

[Hardware Configuration of Host 401]

FIG. 5 is a block diagram of a hardware configuration of the host 401.

The host 401 including the typical personal computer as described aboveincludes a CPU 501, a ROM 502, a RAM 503, a nonvolatile storage 504, adisplay unit 505, an operation unit 506, and the near fieldcommunication unit 402, these units being connected to a bus 507. Thenear field communication unit 402 is hardware for performing near fieldcommunication with the electrical stimulation device 100. Thenon-volatile storage 504 stores an OS and the application program foroperating the personal computer as the host 401 of the electricalstimulation device 100.

[Hardware Configuration of Electrical Stimulation Device 100]

FIG. 6 is a block diagram of a hardware configuration of the electricalstimulation device 100. A CPU 602, a ROM 603, a RAM 604, an A/Dconverter 605, and a second serial interface 606 (in FIG. 6, abbreviatedas a “second serial I/F”) connected to a bus 601 form a well-knownone-chip microcomputer 607.

Anodes of the infrared light emission elements 221 a, 222 a, . . . , 228a as the infrared LEDs forming the muscle displacement sensors 221, 222,. . . , 228 are connected to a power source voltage node +Vcc. Cathodesof the infrared light emission elements 221 a, 222 a, . . . , 228 a areconnected to one end of a current-limiting resistor R609 via a firstmultiplexor 608. The other end of the current-limiting resistor R609 isconnected to ground.

Collectors of the infrared light receiving elements 221 b, 222 b, . . ., 228 b as the phototransistors forming the muscle displacement sensors221, 222, . . . , 228 are connected to the power source voltage node+Vcc. Emitters of the infrared light receiving elements 221 b, 222 b, .. . , 228 b are connected to the A/D converter 605 via a secondmultiplexor 610, and are connected to ground via resistors R611 a, R611b, . . . , R611 h.

The first multiplexor 608 and the second multiplexor 610 are switchablycontrolled at regular intervals in response to a control signal from thesecond serial interface 606. In this manner, eight voltage signals ofthe muscle displacement sensors 221, 222, . . . , 228 are input to theA/D converter 605 in a time-division manner. The first multiplexor 608and the second multiplexor 610 can be collectively referred to as a“sensor multiplexor” configured to select one of the multiple muscledisplacement sensors 221, 222, . . . , 228.

A well-known six-axis sensor 612 and a near field communication unit 613are also connected to the bus 601 of the one-chip microcomputer 607, andorientation information and acceleration information output from thesix-axis sensor 612 are, together with information on eight muscledisplacement sensors 221, 222, . . . , 228 as obtained via the A/Dconverter 605, transmitted to the host 401 via the near fieldcommunication unit 613.

A first serial interface 614 (in FIG. 6, abbreviated as a “first serialI/F”) is further connected to the bus 601 of the one-chip microcomputer607. Note that the first serial interface 614 supplies power to thenot-shown storage battery, and therefore, is used for updating thefirmware stored in the ROM 603.

A booster circuit 615 including a well-known choke coil, a well-knowncapacitor, and a well-known transistor switch is further connected tothe second serial interface 606. A square-wave pulse signal with avoltage substantially equal to the power source voltage +Vcc is, with,e.g., 100 kHz, supplied to the booster circuit 615 from the secondserial interface 606, This square-wave pulse signal performs ON/OFFcontrol for the not-shown transistor switch in the booster circuit 615.

Then, the voltage of the square-wave pulse signal is increased to doubleby the booster circuit 615. An electrical stimulation voltage outputfrom the booster circuit 615 is supplied to the electrodes 201, 202, . .. , 208 via a PWM switch 616 and a third multiplexor 617.

The PWM switch 616 is controlled by the second serial interface 606,thereby performing PWM modulation for the electrical stimulation voltageincreased by the booster circuit 615. The duty ratio of the electricalstimulation voltage changes by PWM modulation, and therefore, theelectrical stimulation voltage applied to the muscle is changed to adesired voltage. The third multiplexor 617 is also controlled via thesecond serial interface 606, Accordingly, the electrode specified by thecommand received from the host 401 via the near field communication unit613 is selected, and the electrical stimulation voltage subjected to PWMmodulation is applied to such an electrode.

It can be also said that the third multiplexor 617 is an electrodemultiplexor configured to select one of the multiple electrodes 201,202, . . . , 208.

[Software Functions of Electrical Stimulation Device 100 and Host 401 inNormal Mode]

FIG. 7 is a block diagram of software functions of the electricalstimulation device 100 and the host 401 in the normal mode.

The electrical stimulation device 100 is an input/output terminal devicehaving the function of transmitting, to the host 401, fluctuation in theuser's arm muscles and the orientation and acceleration of theelectrical stimulation device 100 itself and the function of providingthe electrical stimuli to the muscles of the user's arm according to thecommand received from the host 401.

That is, analog signals output from eight muscle displacement sensors221 to 228 are converted into the muscle displacement information by theA/D converter 605, and together with the orientation information and theacceleration information output from the six-axis sensor 612, aretransmitted to the host 401 via an input/output control unit 701 and anear field communication transmission unit 702.

When receiving the muscle displacement information, the orientationinformation, and the acceleration information from the electricalstimulation device 100 via a near field communication receiving unit711, the host 401 supplies these types of information to an input/outputcontrol unit 712. The input/output control unit 712 is configured tosupply, after having received from the electrical stimulation device100, the muscle displacement information, the orientation information,and the acceleration information to an information processing unit 715as a predetermined application program such as a game and to outputpredetermined screen drawing information to the display unit 505 basedon drawing information output from the information processing unit 715.Moreover, the input/output control unit 712 is configured to transmitelectrical stimulation information output from the informationprocessing unit 715 to the electrical stimulation device 100 via a nearfield communication transmission unit 714.

When receiving, via a near field communication receiving unit 704, theelectrical stimulation execution command output from the host 401, afinger-electrode correspondence conversion unit 703 of the electricalstimulation device 100 refers to an electrode probability matrix 705held in the RAM 604. Then, a finger number specified by the command isconverted into an electrode number, and the PWM switch 616 and the thirdmultiplexor 617 are controlled such that the electrical stimulationvoltage is applied to a desired one of the electrodes 201 to 208.

Note that details of the electrode probability matrix 705 will bedescribed later with reference to FIG. 9 and subsequent figures thereof.

Note that the input/output control unit 701 configured to control theoperation timing of the first multiplexor 608 and the second multiplexor610 for performing the operation of switching the muscle displacementsensors 221 to 228 and the finger-electrode correspondence conversionunit 703 configured to control the operation timing of the thirdmultiplexor 617 for performing the operation of switching the electrodesare fully in asynchronous with each other. Thus, in FIG. 7, theinput/output control unit 701 and the finger-electrode correspondenceconversion unit 703 are illustrated as separate functional blocks.

[Software Functions of Electrical Stimulation Device 100 and Host 401 inCalibration Mode]

FIG. 8 is a block diagram of software functions of the electricalstimulation device 100 and the host 401 in the calibration mode.

Differences of the software functions of the electrical stimulationdevice 100 and the host 401 as illustrated in FIG. 8 from those of FIG.7 are:

<1> the function of the six-axis sensor 612 unnecessary for thecalibration mode is stopped;

<2> the input/output control unit 712 of the host 401 stores a sensorvalue in a sensor value storage unit 801 provided in the RAM 503 or thenon-volatile storage 504 and produces or updates the electrodeprobability matrix 705 to transmit the electrode probability matrix 705to the electrical stimulation device 100; and<3> the electrical stimulation device 100 provides, based on the commandtransmitted from the host 401, the electrical stimulus to the selectedelectrode to synchronously scan the muscle displacement sensors 221 to228.

Specifically for <3>, the input/output control unit 701 of theelectrical stimulation device 100 starts up a built-in timer 803 afterthe electrical stimulus has been provided to the electrode based on thecommand transmitted from the host 401. After a lapse of a predeterminedtime, the muscle displacement sensors 221 to 228 are scanned.

Meanwhile, based on information, which has been received from theelectrical stimulation device 100, on the muscle displacement sensors221 to 228, the input/output control unit 712 of the host 401 acquiresan arithmetic result of a probability arithmetic unit 802 to produce orupdate the electrode probability matrix 705. Then, the produced orupdated electrode probability matrix 705 is transmitted to theelectrical stimulation device 100 via the near field communicationtransmission unit 714. Moreover, the input/output control unit 712 ofthe host 401 displays, during execution of the calibration mode, aprogress in the calibration mode on the display unit 505 by apredetermined message, for example.

[Software Operation of Host 401 in Calibration Mode]

The electrode probability matrix 705 is matrix data indicating acorrespondence among electrodes corresponding to the muscles for movingthe user's fingers and finger motion. FIG. 17 illustrates one example ofa generalized electrode probability matrix 705. The vertical axis (therow) of the electrode probability matrix 705 indicates an electrode, andthe horizontal axis (the column) of the electrode probability matrix 705indicates finger motion. A Bayesian posterior probability by Bayesianestimation is stored in each element.

In the normal mode, when receiving the command for moving a desiredfinger from the host 401, the finger-electrode correspondence conversionunit 703 of the electrical stimulation device 100 refers to theelectrode probability matrix 705 based on finger information specifiedby the host 401. That is, the row of the electrode probability matrix705 corresponding to the finger information and specified by the host401 is referred. The probability is stored in each element forming sucha row. The electrode corresponding to the element indicating the maximumprobability among these elements is an electrode with the highestprobability of moving the finger. As described above, thefinger-electrode correspondence conversion unit 703 converts the fingerspecified by the host 401 into the electrode number, and based on suchinformation, controls the third multiplexor 617.

When the electrical stimulation voltage is provided to a certainelectrode, a predetermined muscle is stimulated, and the fingercorresponding to such a muscle moves. Then, a certain muscledisplacement sensor detects such muscle displacement, and the bentfinger is determined with reference to correspondence data stored in thesensor value storage unit 801. That is, a relationship between fingermotion and the electrode is in a one-to-one correspondence.

It has been, with reference to FIG. 2, described that eight electrodesother than the ground electrodes and eight muscle displacement sensorsare provided on the electrode arrangement surface 100 a of theelectrical stimulation device 100. As described above, a reason whyeight electrodes and eight muscle displacement sensors are provided forfive fingers is that the individual difference in the person's armthickness is absorbed only by the single electrical stimulation device100. Thus, some of these electrodes do not correspond to finger motion.That is, for accurately operating the electrical stimulation device 100,the correspondence among, actual finger motion and the electrodes needsto be clarified by the calibration process.

FIG. 9 is a time chart of the flow of calibration operation executed bythe electrical stimulation device 100 and the host 401 in thecalibration mode.

When the electrical stimulation device 100 is attached to the users arm,muscle displacement sensors detect that the skin of the user comes closeto detection regions of the muscle displacement sensors. When it isdetected that the electrical stimulation device 100 is attached to theuser's arm (S901), the input/output control unit 701 of the electricalstimulation device 100 requests communication establishment from thehost 401 via the near field communication unit 613 (S902). In responseto the communication request from the electrical stimulation device 100,the host 401 replies a status message indicating communicationestablishment (S903). The electrical stimulation device 100 receives thestatus message from the host 401, and replies, to the host 401, a statusmessage indicating that communication establishment has been recognized(S904).

When receiving the status message indicating recognition ofcommunication establishment from the electrical stimulation device 100via the near field communication receiving unit 704, the input/outputcontrol unit 712 of the host 401 starts the process of calibrating themuscle displacement sensors. First, video data named a “resting stateguide video” stored in the non-volatile storage 504 of the host 401 isreproduced and displayed in the display unit 505. Then, a command forcollecting data of the muscle displacement sensors is transmitted to theelectrical stimulation device 100 (S905). The “resting state guidevideo” is video data displaying an illustration of a relaxing hand whenthe electrical stimulation device 100 is attached to a forearm and amessage of “Please wait while relaxing your hand.” When receiving thecommand from the host 401, the electrical stimulation device 100 repliesthe data of all muscle displacement sensors to the host 401 (S906). Themuscle displacement sensor value at this point is a muscle displacementsensor value in a state in which the user's fingers are relaxed, and isa reference value for detecting whether or not the muscle is relaxed.

When receiving the data of eight muscle displacement sensors from theelectrical stimulation device 100, the host 401 stores such data as“resting state data” (S907). Next, video data named a “first operationguide video” stored in the non-volatile storage 504 of the host 401 isreproduced, and is displayed on the display unit 505. Then, the commandfor collecting the data of the muscle displacement sensors istransmitted to the electrical stimulation device 100 (S908). The “firstoperation guide video” is video data displaying an illustration of thehand with a thumb being bent when the electrical stimulation device 100is attached to the forearm and a message of “Please wait while bendingyour thumb.” When receiving the command from the host 401, theelectrical stimulation device 100 replies the data of all muscledisplacement sensors to the host 401 (S909). The muscle displacementsensor value at this point is a muscle displacement sensor value in astate in which the user's thumb is not relaxed.

When receiving the data of eight muscle displacement sensors from theelectrical stimulation device 100, the host 401 stores such data as“first operation state data” (S910). Next, video data named a “secondoperation guide video” stored in the non-volatile storage 504 of thehost 401 is reproduced, and is displayed on the display unit 505. Then,the command for collecting the data of the muscle displacement sensorsis transmitted to the electrical stimulation device 100 (S911). The“second operation guide video” is video data displaying an illustrationof the hand with the index finger being bent when the electricalstimulation device 100 is attached to the forearm and a message of“Please wait while bending your index finger.”

After the step S911, operation corresponding to the steps S908, S909,S910 is, starting from the step S908, performed eight times in total. Atthis point, the video data reproduced by the host 401 and the datareceived from the electrical stimulation device 100 by the host 401 andstored in the sensor value storage unit 801 are as follows:

“First Operation Guide Video”: operation guide in the state in which thethumb is bent, and the first operation state data is stored;

“Second Operation Guide Video”: operation guide in the state in whichthe index finger is bent, and the second operation state data is stored;

“Third Operation Guide Video”: operation guide in a state in which themiddle finger is bent, and third operation state data is stored;

“Fourth Operation Guide Video”: operation guide in a state in which thering finger or the little finger is bent, and fourth operation statedata is stored;

“Fifth Operation Guide Video”: operation guide in a state (palmarflexion) in which the wrist is bent toward the direction of the palmwith the hand extending straight, and fifth operation state data isstored;

“Sixth Operation Guide Video”: operation guide in a state (dorsalflexion) in which the wrist is bent toward the direction of the backhandwith the hand extending straight, and sixth operation state data isstored;

“Seventh Operation Guide Video”: operation guide in a state (radialflexion) in which the wrist is bent toward the direction of the thumbwith the hand extending straight, and seventh operation state data isstored; and

“Eighth Operation Guide Video”: operation guide in a state (ulnarflexion) in which the wrist is bent toward the direction of the littlefinger with e hand extending straight, and eighth operation state datais stored.

When receiving the data of eight muscle displacement sensors from theelectrical stimulation device 100, the host 401 stores such data as the“seventh operation state data” (S912). Next, the video data named the“eighth operation guide video” stored in the non-volatile storage 504 ofthe host 401 is reproduced, and is displayed on the display unit 505.Then, the command for collecting the data of the muscle displacementsensors is transmitted to the electrical stimulation device 100 (S913).The “eighth operation guide video” is video data displaying anillustration of the hand in the state in which the wrist is bent towardthe direction of the little finger (ulnar flexion) with the handextending straight when the electrical stimulation device 100 isattached to the forearm and a message of “Please wait while extendingyour hand straight and bending your wrist toward the direction of thelittle finger.” When receiving the command from the host 401, theelectrical stimulation device 100 replies the data of all muscledisplacement sensors to the host 401 (S914). The muscle displacementsensor value at this point is a muscle displacement sensor value in theulnar flexion state in which the user bends the wrists toward thedirection of the little finger.

When receiving the data of the muscle displacement sensors from theelectrical stimulation device 100, the host 401 stores such data as the“eighth operation state data” (S915).

As described above, the host 401 grasps a correspondence betweenfluctuation in the muscle displacement sensor value and finger motionthrough the step S905 to the step S915.

When the step S915 ends, the input/output control unit 712 of the host401 calculates a relative value of each muscle displacement sensor.Specifically, a first reference value according to the thumb bendingstate is obtained in such a manner that the resting state data issubtracted from the first operation state data. A second reference valueaccording to the index finger bending state is obtained in such a mannerthat the resting state data is subtracted from the second operationstate data. Similarly, a third reference value according to the middlefinger bending state, a fourth reference value according to the ring orlittle finger bending state, a fifth reference value according to thepalmar flexion state, a sixth reference value according to the dorsalflexion state, a seventh reference value according to the radial flexionstate, and an eighth reference value according to the ulnar flexionstate are obtained. These first to eighth reference values form a groupof the relative values of eight muscle displacement sensors. Theinput/output control unit 712 of the host 401 stores these first toeighth reference values in the sensor value storage unit 801.

Next, the input/output control unit 712 of the host 401 multiplies thesefirst to eighth reference values by a predetermined ratio to obtainthresholds. The ratio to be multiplied by the first to eighth referencevalues is herein 50%, for example. The input/output control unit 712 ofthe host 401 also stores these thresholds in the sensor value storageunit 801.

The intensity of reflected light detected by the phototransistor of themuscle displacement sensor greatly varies according to factors(uncertainties) such as the states of the user's skin and muscleopposing the muscle displacement sensor and a relative positionrelationship between the muscle displacement sensor and the user's skin.For this reason, the input/output control unit 712 of the host 401stores, in the sensor value storage unit 801, the muscle displacementsensor values in a state in which the user's fingers are mostly relaxedand in a state in which a user's specific finger is bent, and calculatesa difference between these values. Since the obtained reference valuesare the relative variations of the muscle displacement sensors,influence of the uncertainties can be eliminated.

The A/D converter 605 configured to digitalize the analog signal outputfrom the muscle displacement sensor is, for example, a 10-bit unsignedinteger (0 to 1023). It has been found that when the inventors producethe electrical stimulation device 100 on trial, the relative variationobtained from the muscle displacement sensor having detecteddisplacement of the muscle is around 300 to 900.

After a later-described step S916, the resting state data is subtractedfrom the data of each muscle displacement sensor received by the host401 from the electrical stimulation device 100, and in this manner suchdata of the muscle displacement sensor is converted into the relativevalue of the muscle displacement sensor. Then, an input/output devicecompares the relative value of the muscle displacement sensor with thethreshold to determine whether or not a predetermined finger has moved.

The host 401 having grasped the correspondence between fluctuation inthe muscle displacement sensor value and finger motion through the stepsS905 to S915 subsequently begins the process of grasping thecorrespondence among the electrodes and finger motion.

The input/output control unit 712 of the host 401 transmits, to theelectrical stimulation device 100, a command for collecting the data ofthe muscle displacement sensors after the electrical stimulation voltagehas been applied to the first electrode (S916). When receiving thecommand from the host 401, the electrical stimulation device 100 appliesthe electrical stimulation voltage to the first electrode (S917), andafter a lapse of a predetermined time, collects the data of the muscledisplacement sensors to return such data to the host 401 (S918).

When receiving the data of the muscle displacement sensors from theelectrical stimulation device 100, the input/output control unit 712 ofthe host 401 stores, as sensor value data in the first electrode, thedata in the sensor value storage unit 801 (S919). Next, the input/outputcontrol unit 712 of the host 401 transmits, to the electricalstimulation device 100, a command for collecting the data of the muscledisplacement sensors after the electrical stimulation voltage has beenapplied to the second electrode (S920).

After the step S920, operation corresponding to the steps S916, S917,S918, S919 is, starting from the step S916, performed eight times intotal. At this point, the command transmitted to the electricalstimulation device 100 by the host 401 and the data received by the host401 from the electrical stimulation device 100 and stored in the sensorvalue storage unit 801 are as follows:

the command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the firstelectrode: the sensor value data in the first electrode is stored;

the command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the secondelectrode: sensor value data in the second electrode is stored;

a command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the thirdelectrode: sensor value data in the third electrode is stored;

a command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the fourthelectrode: sensor value data in the fourth electrode is stored;

a command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the fifthelectrode: sensor value data in the fifth electrode is stored;

a command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the sixthelectrode: sensor value data in the sixth electrode is stored;

a command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the seventhelectrode: sensor value data in the seventh electrode is stored; and

a command for collecting the data of the muscle displacement sensorsafter the electrical stimulation voltage has been applied to the eighthelectrode: sensor value data in the eighth electrode is stored.

When receiving the data of the muscle displacement sensors from theelectrical stimulation device 100, the input/output control unit 712 ofthe host 401 stores, as the sensor value data in the seventh electrode,the data in the sensor value storage unit 801 (S921). Next, theinput/output control unit 712 of the host 401 transmits, to theelectrical stimulation device 100, the command for collecting the dataof the muscle displacement sensors after the electrical stimulationvoltage has been applied to the eighth electrode (S922).

When receiving the command from the host 401, the electrical stimulationdevice 100 applies the electrical stimulation voltage to the eighthelectrode (S923), and after a lapse of the predetermined time, collectsthe data of the muscle displacement sensors to return such data to thehost 401 (S924).

When receiving the data of the muscle displacement sensors from theelectrical stimulation device 100, the input/output control unit 712 ofthe host 401 stores, as the sensor value data in the eighth electrode,the data in the sensor value storage unit 801 (S925). Next, theinput/output control unit 712 of the host 401 generates or updates thefirst to eighth operation state data corresponding to motion of eachfinger as stored in a series of operation from the steps S905 to S915and the sensor value data in each electrode as stored in a series ofoperation from the steps S916 to S925.

Note that as a result of execution of a first learning mode (describedlater with reference to FIG. 10 and subsequent figures), if theelectrode probability matrix 705 is present in the host 401, suchupdating is also performed for the electrode probability matrix 705through the probability arithmetic unit 802, The input/output controlunit 712 of the host 401 transmits the generated or updated electrodeprobability matrix 705 to the electrical stimulation device 100 (S926).Then, the electrical stimulation device 100 stores, in the RAM 503, theelectrode probability matrix 705 received from the host 401 (S927), andends a series of processing.

The steps S905 to S915 of FIG. 9 are a muscle displacement sensorcalibration mode for clarifying a correlation among the muscledisplacement sensors and finger motion. The input/output control unit712 of the host 401 executes the muscle displacement sensor calibrationmode, and in this manner, it is clarified from the data obtained fromthe muscle displacement sensors 221 to 228 which finger is currentlymoving.

The steps S916 to S927 surrounded by a dashed line in FIG. 9 are thelearning mode for clarifying a correlation among the electrodes andfinger motion by production and updating of the electrode probabilitymatrix 705. The input/output control unit 712 of the host 401 executesthe learning mode, and in this manner, it is clarified to whichelectrode of the electrodes 201 to 208 the electrical stimulationvoltage needs to be applied to move a desired finger.

That is, the calibration mode includes the muscle displacement sensorcalibration mode and the learning mode. Hereinafter, the learning modewill be described with reference to FIG. 10.

FIG. 10 is a flowchart of the flow of operation of the initial learningmode executed by the host 401 when the user wears the electricalstimulation device 100 for the first time.

When the processing begins (S1001), the input/output control unit 712 ofthe host 401 first initializes a counter variable i to 1, andinitializes all elements of the electrode probability matrix 705 to “0”(S1002).

Subsequent processing is executed in a loop. The input/output controlunit 712 of the host 401 transmits, to the electrical stimulation device100, the command for collecting the data of the muscle displacementsensors after the electrical stimulation voltage has been applied to ani-th electrode (S1003). Then, the input/output control unit 712 of thehost 401 calculates the difference value from the data of the muscledisplacement sensors received from the electrical stimulation device 100to compare such a value with the threshold, thereby checking whether ornot finger motion occurs (S1004) In a case where it is detail tined thatany finger has moved by the electrical stimulus by the i-th electrode(YES at S1005), the input/output control unit 712 of the host 401 stores“1” in the element of the electrode probability matrix 705 in an x-throw corresponding to the x-th finger whose motion has been detected andan i-th column corresponding to the i-th electrode (S1006).

After the step S1006 has been executed or in a case where it is, at thestep S1005, determined that any finger is not moved by the electricalstimulus by the i-th electrode (NO at S1005), the input/output controlunit 712 of the host 401 whether or not the counter variable i reachesthe maximum value of i, i.e., the total number of electrodes. In a casewhere the counter variable i does not reach the total number ofelectrodes (NO at S1007), the input/output control unit 712 of the host401 increments the counter variable i by one (S1008), and repeats theprocessing again from the step S1003.

At the step S1007, in a case where the counter variable i reaches thetotal number of electrodes (YES at S1007), the input/output control unit712 of the host 401 saves the produced electrode probability matrix 705in the non-volatile storage 504, and transmits the electrode probabilitymatrix 705 to the electrical stimulation device 100 (S1009). Then, theinput/output control unit 712 of the host 401 ends a series ofprocessing (S1010).

Subsequently, operation of the step S1003 will be additionallydescribed.

FIG. 11 is a time chart for describing the electrical stimulus, a musclecontraction state, and muscle displacement sensor operation.

Beginning at the top, in FIG. 11, (A) is the electrical stimulus appliedto the electrode, (B) is the muscle contraction state, (C) is a gatesignal indicating an operation period of the muscle displacement sensorin the input/output control unit 712, (D) is an operation period of thefirst muscle displacement sensor, (E) is an operation period of thesecond muscle displacement sensor, (F) is an operation period of thethird muscle displacement sensor, (G) is an operation period of theseventh muscle displacement sensor, and (H) is an operation period ofthe eighth muscle displacement sensor. Only for (B) the musclecontraction state, the vertical axis represents the amount ofdisplacement in muscle contraction. For other items, the vertical axisrepresents a logical value.

When the electrical stimulus is applied to the electrode at a time pointT1101, the muscle starts contracting. From a time point T1102 at whichmuscle contraction becomes stable, the gate signal shows true of thelogic. In response, scanning of the muscle displacement sensors begins.A time necessary for data collection from a single muscle displacementsensor is elapsed within about several msec to about several tens ofmsec. At a time point T1103 at which scanning for all of the muscledisplacement sensors 221 to 228 ends, the logic of the gate signal isinverted to false. At the same time, application of the electricalstimulation voltage to the electrode also ends.

The operation of applying the electrical stimulation voltage to theelectrode to scan the muscle displacement sensors 221 to 228 asillustrated in FIG. 11 is executed for all of eight electrodes.

A human muscle contracts when receiving an electrical stimulationvoltage from the outside through an electrode. It takes about 0.1seconds until the muscle contracts to a predetermined contraction amountand becomes stable after application of the electrical stimulationvoltage. In the electrical stimulation device 100 according to theembodiment of the present invention, a margin time of 0.2 seconds isprovided in expectation of a further margin. The margin time is a timeuntil the time point T1102 at which muscle contraction becomes stableafter the time point T1101 at which the electrical stimulation voltageis applied in FIG. 11.

Next, the electrode probability matrix 705 produced by the processingfrom the steps S1003 to S1008 will be described.

FIG. 12A is a view for describing a matrix indicating finger motion inresponse to the electrical stimulus. Hereinafter, such a matrix will bereferred to as a “finger behavior matrix.”

FIG. 12B is a view of the procedure of selecting an effective electricalstimulus from the finger behavior matrix.

FIG. 12C is a view for describing a matrix indicating a result ofselection of the effective electrical stimulus from the finger behaviormatrix. Such a matrix will be referred to as a “flag matrix.”

FIG. 12D is a view of the electrode probability matrix 705 generatedfrom the flag matrix.

At the step S1004, the input/output control unit 712 calculates thedifference values for the muscle displacement sensors. Then, thedifference values, which correspond to finger motion, for the muscledisplacement sensors are derived. In a case where only a single muscledisplacement sensor corresponds to certain finger motion, the differencevalue is directly employed. In a case where a combination of two or moremuscle displacement sensors corresponds to certain finger motion, theaverage of the difference values for the muscle displacement sensors isemployed. In this manner, numeric values illustrated in FIG. 12A arestored as elements of the finger behavior matrix.

Beginning at the top, the rows of the finger behavior matrix illustratedin FIGS. 12A and 12B, the rows of the flag matrix illustrated in FIG.12C, and the rows of the electrode probability matrix 705 illustrated inFIG. 12D are as follows:

the first row: the state in which the thumb is bent, i.e., the thumbbending state;

the second row: the state in which the index finger is bent, i.e., theindex finger bending state;

the third row: the state in which the middle finger is bent, i.e., themiddle finger bending state;

the fourth row: the state in which the ring finger or the little fingeris bent, i.e., the ring or little finger bending state;

the fifth row: the state (palmar flexion) in which the wrist is benttoward the direction of the palm with the hand extending straight, i.e.,a wrist palmar flexion state;

the sixth row: the state (dorsal flexion) in which the wrist is benttoward the direction of the backhand with the hand extending straight,i.e., a wrist dorsal flexion state;

the seventh row: the state (radial flexion) in which the wrist is benttoward the direction of the thumb with the hand extending straight,i.e., a wrist radial flexion state; and

the eighth row: the state (ulnar flexion) in which the wrist is benttoward the direction of the little finger with the hand extendingstraight, i.e., a wrist ulnar flexion state.

The columns of the finger behavior matrix illustrated in FIGS. 12A and12B, the columns of the flag matrix illustrated in FIG. 12C, and thecolumns of the electrode probability matrix 705 illustrated in FIG. 12Dare, in the order from the left to the right, first to eighth electricalstimuli.

Next, the procedure of determining whether or not the finger has movedat the step S1004 of FIG. 10 will be described.

Focusing on the element in the first row and the first column to theelement in the eighth row and the first column in the finger behaviormatrix illustrated in FIG. 12B, elements of “595 115 92 0 0 0 0 0” areformed in the order from the top. Of these elements in this column, theelement showing the maximum value is “595” in the first row and thefirst column. This value is stored in a maximum value array 1201. Themaximum value array 1201 is an array for storing the maximum value ineach column.

The position of the element “595” is (1, 1) of the finger behaviormatrix, and such a row (the first row) corresponds to the thumb bendingstate. Thus, it is determined whether or not the value “595” exceeds thethreshold for the thumb bending state. As a result of determination, itis determined that the value exceeds the threshold. Thus, the element inthe first row and the first column in the finger behavior matrix istaken as effective, and true of the logic is stored in a flag array1202. In FIG. 12B, such an element is represented by a white circle.

As described above, the maximum value is selected for each row in thefinger behavior matrix, and is stored in the maximum value array 1201.Then, such a value is compared with the threshold in finger movement towhich the element belongs based on the position of the element. As aresult of comparison, when the maximum value is a value equal to orgreater than the threshold, true of the logic is stored in the flagarray 1202. Then, the element at the same position in the flag matrix asthe position of the element of the maximum value array 1201corresponding to true of the logic in the flag array 1202 is taken astrue of the logic. This is the flag matrix of FIG. 12C.

The element with true of the logic in the flag matrix has a probabilityof 100% (=1). This is the electrode probability matrix 705 of FIG. 12D.

The electrode probability matrix 705 is a matrix indicating which fingerto be moved and the probability of moving of the finger when theelectrical stimulation voltage is provided to a certain electrode. Theprobability stored as the element of the electrode probability matrix705 is a posterior probability by, e.g., Bayesian estimation. That is,production of the electrode probability matrix 705 in the flowchart ofFIG. 10 is initial learning in Bayesian estimation.

At the point of time of execution of the flowchart of FIG. 10, theprocessing is still in initial learning. Thus, only any of 0 or 1 ispresent. These values fluctuate in a second learning mode or later asdescribed below.

FIGS. 13 and 14 are flowcharts of the flow of operation of the secondlearning mode or later executed by the host 401 when the user wears theelectrical stimulation device 100 for the second time or later.

When the processing begins (S130, the input/output control unit 712 ofthe host 401 first initializes a counter variable j to 1, andinitializes a flag variable MFflag to false of the logic (S1302). Theflag variable MFflag is a flag for recording occurrence of a state inwhich the finger is moved by the electrical stimulus.

Subsequent processing is executed in a loop. The input/output controlunit 712 transmits, to the electrical stimulation device 100, thecommand for collecting the data of the muscle displacement sensors afterthe electrical stimulation voltage has been applied to a j-th electrode(S1303). Then, the input/output control unit 712 calculates thedifference value from the data of the muscle displacement sensors fromthe electrical stimulation device 100 to compare such a value with thethreshold, thereby checking whether or not finger motion occurs (S1304).The steps S1303 and S1304 have the same processing contents as those ofthe steps S1003 and S1004 of FIG. 10.

If it is determined that any finger is moved by the electrical stimulusby the j-th electrode (YES at S1305), the input/output control unit 712subsequently checks whether or not the flag variable MFflag is false ofthe logic, “whether or not the finger has first moved at this point oftime.” If it is determined that the finger has first moved at this pointof time (YES at S1306), the electrode probability matrix 705 saved inthe non-volatile storage 504 of the host 401 is read out to the RAM 503,and the elements of the electrode probability matrix 705 on the RAM 503are moved with the rows and/or the columns together (S1307). Since theelements of the electrode probability matrix 705 are moved as describedabove, a relative position relationship among the electrodes of theelectrical stimulation device 100 currently attached to the arm of theuser and the muscles is reflected in the electrode probability matrix705.

Next, the input/output control unit 712 operates the probabilityarithmetic unit 802 to perform arithmetic processing of the Bayesianposterior probability “P(x|j)” of not moving the finger for the elementsof the electrode probability matrix 705 corresponding to the first toj−1st electrodes, and updates the corresponding element of the electrodeprobability matrix 705 (S1308). Then, the flag variable MFflag isshifted to true of the logic (S1309), and the processing transitions toa step S1410 of FIG. 14. That is, after it has been determined, at thestep S1305, that any finger has moved (YES at S1305), MFflag is shiftedto true of the logic at the step S1306, and therefore, the processingtransitions to the step S1410 of FIG. 14 without performing theprocessing of the steps S1307, S1308, and S1309.

Next, movement of the elements of the electrode probability matrix 705at the step S1307 will be described in detail with reference to FIGS.15A and 15B.

FIG. 15A is a schematic view for describing an arrangement relationshipamong the arm muscles and the electrodes when the user wears theelectrical stimulation device 100 on the arm for the first time.

FIG. 15B is a schematic view for describing the arrangement relationshipamong the arm muscles and the electrodes when the user again wears theelectrical stimulation device 100 on the arm.

In FIG. 15A, an electrode 1501 is apart from a muscle 1502. An electrode1503 is close to the muscle 1502. An electrode 1505 is close to a muscle1504. Note that an electrode 1506 is a ground electrode commonly usedfor the electrode 1501, the electrode 1503, and the electrode 1505.

In comparison between FIG. 15A and FIG. 15B, a relative positionrelationship between the user's arm and the electrode arrangementsurface 100 a of the electrical stimulation device 100 is shifted inFIG. 15B. Thus, the electrode 1501 is close to the muscle 1502, and theelectrode 1503 is close to the muscle 1504. Moreover, the electrode 1505is apart from the muscle 1504.

When the relative position relationship between the user's arm and theelectrode arrangement surface 100 a of the electrical stimulation device100 is shifted as described above, arrangement of the electrodesopposing the muscles also changes. Such a phenomenon occurs asinconsistency among the elements of the finger behavior matrix and theelements of the flag matrix produced based on the finger behaviormatrix. For this reason, the elements of the electrode probabilitymatrix 705 stored in advance in the non-volatile storage 504 need to beadjusted to the detected finger behavior matrix.

FIG. 16A is an example of the finger behavior matrix produced in thesecond learning mode or later.

FIG. 16B is a virtual electrode probability matrix 705 produced based onthe finger behavior matrix of FIG. 16A.

FIG. 16C is the electrode probability matrix 705 of FIG. 12D.

FIG. 16D is a matrix obtained by rearrangement of the electrodeprobability matrix 705 of FIG. 16C.

First, the electrode probability matrix 705 of FIG. 16C is, as describedwith reference to FIG. 12D, the matrix data produced in the firstlearning mode. On the other hand, the virtual electrode probabilitymatrix 705 illustrated in FIG. 16B is matrix data produced in the secondlearning mode or later.

Only by comparison of the matrix data, it seems that the degree of shiftof the relative position relationship (FIG. 16B) between the user's armand the electrical stimulation device 100 in the second learning modefrom the relative position relationship (FIG. 16C) between the user'sarm and the electrical stimulation device 100 in the first learning modeis not noticeable. However, focusing on the element, which indicatesthat the finger has moved, on the upper left side of the matrix data, aposition shift between the position (P1603) of the element at the pointof time of initial finger movement in the first learning mode and theposition (P1601) of the element at the point of time of initial fingermovement in the second learning mode is clearly shown. That is, theshift between the relative position relationship between the user's armand the electrical stimulation device 100 at a previous use point andthe relative position relationship between the user's arm and theelectrical stimulation device 100 at a current point is clearly shown asan element position shift.

As described earlier, the electrode probability matrix 705 is the matrixdata indicating, in teams of probability, the correlation among theelectrodes and finger motion. The Bayesian posterior probability byBayesian estimation is applied as the probability. However, if the shiftbetween the relative position relationship between the user's arm andthe electrical stimulation device 100 at the previous use point and therelative position relationship between the user's arm and the electricalstimulation device 100 at the current point remains in the electrodeprobability matrix 705 before Bayesian estimation, the accuracy oflearning is significantly lowered. For this reason, the input/outputcontrol unit 712 of the host 401 interchanges, in association with therelative position relationship between the user's arm and the electricalstimulation device 100 at the current point, the row and column elementsof the electrode probability matrix 705 read out from the non-volatilestorage 504 and held in the RAM 503. In the case of FIG. 16C, the columnof the electrode probability matrix 705 of FIG. 16C is shifted to theright by one such that the position (1, 1) of the element P1603 is atthe same position as the position (1, 2) of the element P1601 of FIG.16B. Accordingly, an element group A1604 of FIG. 16C is arranged at thesame position as an element group A1602 of FIG. 16B, Then, an elementgroup A1605 of FIG. 16C is shifted out in association with movement ofthe element group A1604, and is arranged in the blank first column ofthe electrode probability matrix 705 at a left end thereof. This is theelectrode probability matrix 705 of FIG. 16D.

Note that the processing of the step S1308 is the processing of updatingthe element group A1605 in FIG. 16D.

For the processing of searching for the element indicating the effectiveelectrical stimulus and positioned on the upper left side of theelectrode probability matrix 705 at the step S1307 of FIG. 13, theelectrode probability matrix 705 is, for the sake of simplicity,configured based on an assumption that motion of the finger with thesmallest number first occurs when the electrical stimulation voltage issequentially applied to the electrodes. Note that this is for the sakeof convenience, and therefore, the element of the electrode probabilitymatrix 705 corresponding to finger motion first detected after theelectrical stimulation voltage has been sequentially applied to theelectrodes may be referred.

Note that in a case where the initially-moved finger is not in the thumbbending state at the step S1306 of FIG. 13, any electrode is not in thethumb bending state in the current relative position relationshipbetween the user's arm and the electrical stimulation device 100. Thatis, arrangement of the electrodes fails to bend the thumb. In this case,the element in the same row of the electrode probability matrix 705corresponding to the initially-moved finger is referred. That is, thefirst row indicating the thumb bending state of the electrodeprobability matrix 705 is ignored. The electrode probability matrix 705is rearranged only in units of columns, but is not rearranged in unitsof rows.

Referring back to FIGS. 13 and 14, the flowchart will be continuouslydescribed.

After the step S1309 or at the step S1306, in the case where the flagvariable MFflag is true of the logic (NO at S1306), the processingtransitions to the processing of FIG. 14.

As illustrated in FIG. 14, the input/output control unit 712 operatesthe probability arithmetic unit 802 to perform arithmetic processing ofthe Bayesian posterior probability “P(x|j)” of moving the finger for theelement indicating that the finger was moved among the elements of theelectrode probability matrix 705 corresponding to the j-th electrode.Moreover, for the element indicating that the finger was not moved,arithmetic processing is performed to obtain the Bayesian posteriorprobability “P(x|j)” of not moving the finger, and the correspondingelement of the electrode probability matrix 705 is updated (S1410).

Then, the input/output control unit 712 checks whether or not thecounter variable j reaches the maximum value of j, i.e., the totalnumber of electrodes. In a case where the counter variable j does notreach the total number of electrodes (NO at S1411) the input/outputcontrol unit 712 increments the counter variable j by one (S1412), andthe processing is repeated again from the step S1303.

In a case where the counter variable j reaches, at the step S1411, thetotal number of electrodes (YES at S1411), the input/output control unit712 saves the produced electrode probability matrix 705 in thenon-volatile storage 504 to transmit the electrode probability matrix705 to the electrical stimulation device 100 (S1413), and ends a seriesof processing (S1414).

Referring back to FIG. 13, in a case where any finger does not move atthe step S1305 (NO at S1305), the input/output control unit 712subsequently checks whether or not the flag variable MFflag is false ofthe logic, i.e., whether or not the finger does not move yet at thispoint (S1415). In a case where the finger does not move yet (YES atS1415), checking of the counter variable j at the step S1411 isperformed without doing anything.

At the step S1415, when the flag variable MFflag is true of the logic,i.e., the finger has already moved at this point (NO at S1415), theinput/output control unit 712 operates the probability arithmetic unit802 to perform the Bayesian posterior probability “P(x|j)” of not movingthe finger for all elements of the electrode probability matrix 705corresponding to the j-th electrode, and updates the correspondingelement of the electrode probability matrix 705 (S1416). Then, checkingof the counter variable j at the step S1411 is performed.

Determination at the step S1415 is the processing of determining whetheror not rearrangement of the electrode probability matrix 705 at the stepS1307 has been performed. As long as the electrode probability matrix705 indicating the relative position relationship between the user's armand the electrical stimulation device 100 at the previous use point isnot adjusted to the relative position relationship between the user'sarm and the electrical stimulation device 100 at the current point,learning by Bayesian estimation cannot be accurately carried out for theelectrode probability matrix 705. Thus, Bayesian estimation arithmeticprocessing is not performed until the processing of the step S1307 iscompleted (YES at S1415), but is performed after the processing of thestep S1307 has been completed (S1308, S1410, NO of S1415 to S1416).

The electrical stimulation device 100 according to the embodiment of thepresent invention includes eight muscle displacement sensors and eightelectrodes, but the number of muscle displacement sensors and the numberof electrodes are not necessarily eight. Rather, a greater number ofmuscle displacement sensors and a greater number of electrodes result infiner detection of the muscle contraction state and finer musclecontraction control.

FIG. 17 is a view of one example of the generalized electrodeprobability matrix 705. Every time the user repeatedly uses theelectrical stimulation device 100, the electrical stimulation device 100is repeatedly attached/detached to/from the user's arm. That is, everytime the electrical stimulation device 100 is attached/detached to/fromthe user's arm, the learning mode is executed. When the learning mode isrepeatedly executed, a correlation between a certain electrode andfinger motion is fixed as a result. For the x rows and the j columns,the Bayesian posterior probability “P(x|j)” is stored in each element ofthe electrode probability matrix 705.

The embodiment of the present invention described above is applicable asfollows.

(1) It is assumed that a single electrical stimulation device 100 isinstalled per household. An arm thickness varies among a father, amother, and a child. Thus, in a case where the single electricalstimulation device 100 is shared by multiple users, a userauthentication function is preferably provided at the host 401, and theelectrode probability matrix 705 is preferably linked to a user ID.

Any type of user authentication may be employed as long as a unit havingthe function of uniquely identifying the user. For example, not onlygeneral password authentication using a keyboard but also biometricauthentication such as fingerprints, veins, and irises can be utilized.It is easy to use a biometric authentication unit using the fingerprintor the vein when such a unit is housed in the circuit housing box 103 ofthe electrical stimulation device 100.

Moreover, when this user authentication function is integrated with auser authentication function of the information processing unit 715 asthe application program, user authentication of the electricalstimulation device 100 and user authentication of the applicationprogram can be unified. Thus, better usability can be expected. In thiscase, the user ID is linked to user data of the information processingunit 715 and the electrode probability matrix 705 of the electricalstimulation device 100.

That is, a device driver program of the electrical stimulation device100 installed in the host 401 contains the user authentication function.The application program utilizes the user authentication function of thedevice driver program so that sharing of the electrical stimulationdevice 100 by multiple users and unification of user authentication canbe realized.

(2) In the flowcharts illustrated in FIGS. 10, 13, and 14, the data ofthe muscle displacement sensors is taken after the electrical stimulushas been provided to the electrode, and then, finger motion is checked.Thereafter, the determination and learning processing sequentiallyproceed. However, the electrical stimulus may be first provided to theelectrode, and then, the process of taking the data of the muscledisplacement sensors may be executed for all electrodes to produce thefinger behavior matrix in advance. Thereafter, the determination andlearning processing may be performed. Needless to say, the step S1307 ofFIG. 13 is also essential in this case.(3) In the electrical stimulation device 100 according to the embodimentof the present invention, Bayesian estimation is employed as a learningalgorithm. However, the learning algorithm is not limited to above. Forexample, other supervised learning algorithms such as a support vectormachine may be used.

In the present embodiment, the electrical stimulation device 100 and theelectrical stimulation system 400 have been disclosed.

For clarifying a correlation between electrical stimulation by theelectrodes and finger motion, the electrode probability matrix 705configured such that the Bayesian posterior probability indicatingfinger motion corresponding to the electrode is described as the elementis produced in the host 401, and is transferred to the electricalstimulation device 100. In the second learning mode or later, foradjusting the previous electrode probability matrix 705 to a currentstate of attachment of the electrical stimulation device 100 to theuser's arm, the position of the element positioned on the upper leftside of the electrode probability matrix 705 and indicating that thefinger has moved is compared, and as necessary, the columns of theelectrode probability matrix 705 are rearranged.

The electrical stimulation device 100 and the host 401 are configured asdescribed above. Thus, the electrical stimulation device 100 and theelectrical stimulation system 400 can be realized, the device and thesystem being configured so that even in the state of attachment to onearm of the user, the correspondence among finger motion and theelectrodes can be clarified in a short amount of time and an intendedfinger can be driven at high accuracy with very few erroneous operation.

The embodiment of the present invention has been described above, butthe present invention is not limited to the above-described embodiment.Other variations and applications are included without departing fromthe gist of the present invention described in the claims.

For example, the above-described embodiment is for specificallydescribing detailed device and system configurations to clearly describethe present invention, and is not necessarily limited to that includingall of the described configurations. Moreover, some of configurations ofa certain embodiment may be replaced with configurations of otherembodiments. Further, configurations of other embodiments may be addedto a certain embodiment. In addition, for some of configurations of eachembodiment, addition/elimination/replacement of other configurations isavailable.

Part or the entirety of each configuration, function, processing unit,etc. as described above may be implemented in hardware by designingusing an integrated circuit, for example. Moreover, each configuration,function, etc. as described above may be implemented in software forinterpreting and executing a program for implementing each function by aprocessor. Information for implementing each function, such as aprogram, a table, and a file, can be held in a recording medium such asa memory, a hard drive, a volatile or non-volatile storage such as asolid state drive (SSD), an IC card, or an optical disk.

Control and information lines assumed as necessary for description areillustrated, and all control and information lines for a product are notnecessarily illustrated. It may be assumed that almost allconfigurations are actually connected to each other.

DESCRIPTION OF REFERENCE SIGNS

-   100 electrical stimulation device-   101 band-   102 left portion-   103 circuit housing box-   104 first serial interface terminal-   150 arithmetic processing unit-   201, 202, 203, 204, 205, 206, 207, 208, 211, 212, 213, 216 electrode-   217 electrode-   221, 223, 227 muscle displacement sensor-   231 right electrode arrangement spot-   232 central electrode arrangement spot-   233 left electrode arrangement spot-   400 electrical stimulation system-   401 host-   402 near field communication unit-   501 CPU-   502 ROM-   503 RAM-   504 non-volatile storage-   505 display unit-   506 operation unit-   507 bus-   601 bus-   602 CPU-   603 ROM-   604 RAM-   605 A/D converter-   606 second serial interface-   607 one-chip microcomputer-   608 first multiplexor-   610 second multiplexor-   612 six-axis sensor-   613 near field communication unit-   614 first serial interface-   615 booster circuit-   616 PWM switch-   617 third multiplexor-   701 input/output control unit-   702 near field communication transmission unit-   703 finger-electrode correspondence conversion unit-   704 near field communication receiving unit-   705 electrode probability matrix-   711 near field communication receiving unit-   712 input/output control unit-   715 information processing unit-   714 near field communication transmission unit-   801 sensor value storage unit-   802 probability arithmetic unit-   803 timer-   1201 maximum value array-   1202 flag array

The invention claimed is:
 1. An electrical stimulation systemcomprising: an electrical stimulation device; and a host configured totransmit, to the electrical stimulation device, a command for moving afinger, wherein the electrical stimulation device includes a bandadapted to be wound around an arm of a user, multiple muscledisplacement sensors arranged on one surface of the band and configuredto detect muscle displacement of the arm of the user, a sensormultiplexor configured to select one of the multiple muscle displacementsensors, multiple electrodes arranged adjacent to the multiple muscledisplacement sensors on the surface of the band on which the multiplemuscle displacement sensors are arranged, an electrode multiplexorconfigured to select one of the multiple electrodes, a near fieldcommunication receiving unit configured to receive the command formoving the finger from the host, a near field communication transmissionunit configured to convert a signal obtained from each muscledisplacement sensor and relating to the muscle displacement of the armof the user into digital data to transmit the digital data to the host,an electrode probability matrix configured such that a correspondenceamong finger motion and the multiple electrodes is described in terms ofprobability, and a finger-electrode correspondence conversion unitconfigured to specify, based on the command for moving the finger, anelectrode with a maximum probability from the electrode probabilitymatrix and to control the electrode multiplexor to select the specifiedelectrode, and the host includes a near field communication receivingunit configured to receive the data of each muscle displacement sensorfrom the electrical stimulation device, the electrode probabilitymatrix, an input/output control unit configured to update an element ofthe electrode probability matrix after a shift of a current relativeposition relationship between the arm of the user and the electricalstimulation device has been detected to rearrange the element of theelectrode probability matrix after the data of each muscle displacementsensor has been converted into the finger motion of the user, and a nearfield communication transmission unit configured to transmit the updatedelectrode probability matrix to the electrical stimulation device. 2.The electrical stimulation system according to claim 1, wherein the hostfurther includes a probability arithmetic unit configured to calculate aposterior probability based on a learning algorithm to update an elementof the electrode probability matrix.